The cultural, educational, political and economic systems of the United States are incapable of sustaining an indigenous first class science and engineering capability.
Recall also that in the first space race, the mostly US designed Vanguard failed miserably. It was the German engineers from Redstone Arsenal that brought us the first successes and generally managed the technical aspects of the space program through Apollo.
Of course, having now shot our wad economically and not being particularly welcome to talent from other countries, the prospects for importing scientists and engineers for a second space program look pretty dim.
That's something so depressingly stupid as to stand out even among all the other depressingly stupid things our government does. Unskilled laborers from Mexico and Central America are welcomed by the million every year while talent is actively turned away.
It's a long night coming.
I think that is more a factor of Vanguard being a NACA (forerunner of NASA) project, while Redstone was military. Now, unfortunately, the NASA culture has bled over into the military one. Only the Air Force seems able to bring a new aircraft design along. They do it by having a competition, a fly off, not just a paper design contest where the best politicians win.